From Wikipedia, the free encyclopedia

Filename extension
.ogv, .ogg
Internet media type
Initial release1 June 2004 (2004-06-01)[1]
Latest release
Theora I
16 March 2011[2]
Type of formatVideo coding format
Contained byOgg, Matroska
Extended fromVP3
Open format?Yes[3]
Free format?Yes[4]
Initial release3 November 2008 (2008-11-03) (1.0)
Stable release
1.1.1 / 1 October 2009; 14 years ago (2009-10-01)[5]
Preview release
1.2.0 Alpha 1 / 24 September 2010; 13 years ago (2010-09-24)[6]
Written inC
Operating systemUnix-like (incl Linux, Mac OS X), Windows
TypeVideo codec, reference implementation
License3-clause BSD

Theora is a free lossy video compression format.[7] It was developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg container.

The libtheora video codec is the reference implementation of the Theora video compression format developed by the Xiph.Org Foundation.[8][9]

Theora was derived from the formerly proprietary VP3 codec, released into the public domain by On2 Technologies. It is broadly comparable in design and bitrate efficiency to MPEG-4 Part 2, early versions of Windows Media Video, and RealVideo while it lacked some of the features present in some of these other codecs. It is comparable in open standards philosophy to the BBC's Dirac codec.

Theora was named after Theora Jones, Edison Carter's Controller on the Max Headroom television program.[10]

Technical details[edit]

Theora is a variable-bitrate, DCT-based video compression scheme. Like most common video codecs, Theora used chroma subsampling, block-based motion compensation and an 8-by-8 DCT block. Pixels are grouped into various structures, namely blocks, super blocks, and macroblocks. Theora supports intra-coded frames ("keyframes") and forward-predictive frames, but not bi-predictive frames which are found in H.264 and VC-1. Theora also does not support interlacing, or bit-depths larger than 8 bits per component.[2]

Theora video streams can be stored in any suitable container format, but they are most commonly found in the Ogg container with Vorbis or FLAC audio streams. This combination provided a completely open, royalty-free multimedia format. It can also be used with the Matroska container.[11]

The Theora video-compression format is compatible with the VP3 video-compression format, which consisted of a backward-compatible superset.[12][13] Theora is a superset of VP3, and VP3 streams (with some minor syntactic modifications) can be converted into Theora streams without recompression (but not vice versa).[13] VP3 video compression can be decoded using Theora implementations, but Theora video compression usually cannot be decoded using old VP3 implementations.


Theora's predecessor On2 TrueMotion VP3 was originally a proprietary and patent-encumbered video codec developed by On2 Technologies. VP3.1 was introduced in May 2000[14] and followed three months later by the VP3.2 release,[15] which was the basis for Theora.

Move to free software[edit]

In August 2001, On2 Technologies announced that they would release an open source version of their VP3.2 video compression algorithm.[16][17] In September 2001, On2 Technologies published the source code of the VP3.2 codec under the VP3.2 Public License 0.1,[18] a custom open-source license.[19][20] The license only granted the right to modify the source code if the resultant larger work continued to support playback of VP3.2 data.[18][21]

In March 2002, On2 responded to the public's reception by relicensing the VP3 codec under the GNU Lesser General Public License.[22] In June 2002, On2 donated VP3 to the Xiph.Org Foundation and offered it under the Ogg Vorbis BSD-style license.[23][24][25][26] On2 also made an irrevocable, royalty-free license grant for any patent claims it might have over the software and any derivatives,[2] allowing anyone to use any VP3-derived codec for any purpose.[12][27] In August 2002, On2 entered into an agreement with the Xiph.Org Foundation to make VP3 the basis of a new, free video codec, called Theora.[28] On2 declared Theora to be VP3's successor.[citation needed] On 3 October 2002, On2 and Xiph announced the completion and availability of the initial alpha code release of libtheora, Theora's reference implementation.[29]

There is no formal specification for VP3's bitstream format beyond the VP3 source code published by On2 Technologies. In 2003, Mike Melanson created an incomplete description of the VP3 bitstream format and decoding process at a higher level than source code, with some help from On2 and Xiph.Org Foundation. The Theora specification adopted some portions of this VP3 description.[2][30]

A successor to Theora, Daala, was later merged into AV1.[31]

Theora I specification[edit]

Example of a Theora video used on Wikipedia, showing a Polikarpov I-15 biplane at an aerobatic display.

The Theora I bitstream format was frozen in June 2004 after the libtheora 1.0alpha3 release.[1] Videos encoded with any version of the libtheora since the alpha3 will be compatible with any future player.[1][32] This is also true for videos encoded with any implementation of the Theora I specification since the format freeze. The Theora I Specification was completely published in 2004.[33] Any later changes in the specification are minor updates.

The Theora reference implementation libtheora spent several years in alpha and beta status.[32] The first alpha version was released on 25 September 2002 and the first beta version was released on 22 September 2007.[34] The first stable release of libtheora was made in November 2008.[35][36] Work then focused on improving the codec's performance in the "Thusnelda" branch, which was released as version 1.1 in September 2009 as the second stable libtheora release.[32][37] This release brought some technical improvements and new features, such as the new rate control module and the two-pass rate control.

The codename for the next version of libtheora was Ptalarbvorm.[38]

Theora was well established as a video format in open-source applications, and became the format used for Wikipedia's video content before replaced by VP9. However, the proposed adoption of Theora as part of the baseline video support in HTML5 resulted in controversy.[39]


In October 2023, Google announced intent to remove Theora support from Chromium (finalizing removal by Google Chrome 123),[40] with Firefox following suit. Google developers claimed that despite lack of adoption, Theora made a case for open and royalty-free codecs like AV1.[41][better source needed]


Encoding performance[edit]

Evaluations of the VP3[42] and early Theora encoders[43][44][45] found that their subjective visual quality was inferior to that of contemporary video codecs. The performance characteristics of the Theora 1.0 reference implementation are dominated mostly by implementation problems inherited from the original VP3 code base.[46] Work that lead up to the 1.1 stable release focused on improving on or eliminating these. A May 2009 review of this work by Xiph developer Chris Montgomery claimed a considerable improvement in quality, both subjectively and as measured by PSNR, by improving the forward DCT and quantisation matrices.[47] More recently however,[when?] Xiph developers compared the 1.1 Theora encoder to YouTube's H.264 and H.263+ encoders, in response to concerns raised in 2009 about Theora's inferior performance by Chris DiBona, a Google employee.[48] They found the results from Theora to be nearly the same as YouTube's H.264 output, and much better than the H.263+ output.[49][50]

The differences in quality, bitrate and file size between a YouTube H.264 video and a transcoded Ogg video file are very small.[51]

Playback performance[edit]

There was an open-source VHDL code base for a hardware Theora decoder in development.[52][needs update] It began as a 2006 Google Summer of Code project, and it has been developed on both the Nios II and LEON processors.[53] However, there are currently no Theora decoder chips in production, and portable media players, smartphones and similar devices with limited computing power rely on such chips to provide efficient playback.


Web browsers[edit]

As originally recommended by HTML 5, these browsers support Theora when embedded by the video element:

Supporting media frameworks[edit]

Supporting applications[edit]


There are several third-party programs that support encoding through libtheora:

Name Description Operating Systems Supported
Unix-like OS X Windows
A command-line program that transcodes video by decoding with FFmpeg and reencoding with libtheora to encode it Yes Yes Yes
Can transcode to single-pass Theora 1.0 and optionally stream it Yes Yes Yes
"Video DJing" software that can encode to and stream Theora Yes Yes ?
The video editor supplied with KDE Yes ? ?
The video editor supplied with GNOME Yes ? ?
Video editing software for Linux. Can edit, encode and stream theora. Yes Yes ?
Can output to Theora only with the Matroska container Yes Yes Yes
Records the screen to Ogg Theora with optional Vorbis audio Yes ? ?

The libtheora library contains the reference implementation of the Theora specification for encoding and decoding. libtheora was developed by the Xiph.Org Foundation. The library was released under the terms of a BSD-style license.

Also, several media frameworks have support for Theora.

  • The open-source ffdshow audio/video decoder is capable of encoding Theora videos using its Video for Windows (VFW) multi-codec interface within popular AVI editing programs.[72][73][74] It supports both encoding and decoding Theora video streams and uses Theora's alpha 4 libraries. However, many of the more refined features of Theora are not available to the user in ffdshow's interface.
  • The GStreamer framework has support for parsing raw Theora streams, encoding and decoding raw Theora streams to/from YUV video[75][76]


Name Description Operating Systems Supported
Unix-like OS X Windows
Video editing software for Linux. Can edit, encode and stream theora. Yes Yes ?
The KDE video editor. Yes ? ?
Yes ? ?
The GNOME video editor. Yes ? ?
CVS versions of the Cinelerra non-linear video editing system support Theora, as of August 2005. Yes Yes ?
oggz-tools by
Command line programs to examine and edit Ogg files. Yes ? Yes
Ogg Video Tools by yornstreamnik
Tools to resize, cut, split, join, and others[77] Yes Yes Yes
AVS Video Editor
? ? Yes


The following streaming media servers are capable of streaming Theora video:

Name Description Operating Systems Supported
Unix-like OS X Windows
Yes Yes Yes
Yes ? Yes
Can stream ogg/theora/vorbis in realtime to a file or fifo. Yes Yes ?


Elphel is the main maker of cameras that record in theora.

See also[edit]


  1. ^ a b c Giles, Ralph (1 June 2004). "Theora I bitstream freeze". theora-dev (Mailing list). Retrieved 25 September 2009.
  2. ^ a b c d "Theora Specification" (PDF). Xiph.Org Foundation. 16 March 2011. Retrieved 31 January 2012.
  3. ^ "PlayOgg! – FSF – Free Software Foundation". 17 March 2010. Retrieved 1 October 2013.
  4. ^ "Theora FAQ". 2016. Archived from the original on 26 September 2020. Retrieved 1 December 2021.
  5. ^ "Theora 1.1.1 release". Xiph.Org Foundation. Retrieved 6 October 2009.
  6. ^ "libtheora 1.2.0alpha1 release". Xiph.Org Foundation. September 2010. Retrieved 10 October 2010.
  7. ^ Theora.
  8. ^ Xiph.Org Foundation. "libtheora Documentation 1.1.0". Xiph.Org Foundation. Retrieved 25 September 2009.
  9. ^ ohloh. "libtheora". ohloh. Archived from the original on 10 October 2010. Retrieved 25 September 2009.
  10. ^ "Theora FAQ". Xiph.Org Foundation. Retrieved 6 August 2009.
  11. ^ "Matroska Codec Specs". Matroska. Retrieved 6 August 2009.
  12. ^ a b libtheora license (Subversion – Trunk), Retrieved on 16 August 2009
  13. ^ a b FAQ – Theora and VP3. Retrieved 2 September 2009
  14. ^ On2 (17 May 2000), Launches Next Generation of Revolutionary Broadband Video Technology, archived from the original on 3 December 2007{{citation}}: CS1 maint: numeric names: authors list (link)
  15. ^ On2 (16 August 2000), On2 Introduces TrueMotion VP3.2, archived from the original on 3 December 2007, retrieved 23 August 2010{{citation}}: CS1 maint: numeric names: authors list (link)
  16. ^ On2 (7 August 2001), On2 Technologies to Open Source VP3.2 Video Compression Technology (archived website), archived from the original on 3 December 2007{{citation}}: CS1 maint: numeric names: authors list (link)
  17. ^ Mariano, Gwendolyn (7 August 2001). "On2's video codec to go open-source". CNET.
  18. ^ a b On2 Technologies (2001), VP3.2 Public License 0.1, Xiph.Org Foundation, archived from the original on 4 April 2016, retrieved 10 February 2008{{citation}}: CS1 maint: numeric names: authors list (link)
  19. ^ Bernat, Bill (7 September 2001). "On2 Offers Up VP3.2 Source Code".
  20. ^ On2 (7 September 2001), On2 Technologies Makes Video Compression Technology Available to Open-Source Community, archived from the original on 7 December 2007{{citation}}: CS1 maint: numeric names: authors list (link)
  21. ^ Seibert, Stan (September 2001). "VP3.2 video codec open sourced". vorbis (Mailing list).
  22. ^ "On2 Alters Licensing Terms for VP3; Company Responds to Open Source Community Demands" (Press release). On2 Technologies. 28 March 2002. Archived from the original on 4 December 2010. Retrieved 16 August 2009.
  23. ^ Xiph.Org Foundation (16 March 2011). "Theora Specification" (PDF). Xiph.Org Foundation. p. 1.
  24. ^ "VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform", On2, 24 June 2002, archived from the original on 3 December 2007
  25. ^ (23 June 2002) Ogg Vorbis, VP3 combining forces to create Open Source multimedia package, Retrieved on 2009-08-16
  26. ^ (24 June 2002) On2 Throws More Open-Source at MPEG-4, Retrieved on 16 August 2009
  27. ^ VP32 codec license (Subversion – Trunk), Retrieved on 16 August 2009
  28. ^ The Free Library (1 August 2002) On2 Signs Pact With to Develop/Support VP3, Retrieved on 16 August 2009
  29. ^ On2 (3 October 2002), On2 and Xiph Announce Alpha Code Release of Theora, VP3-Vorbis-Based Multimedia Solution, archived from the original on 4 December 2007{{citation}}: CS1 maint: numeric names: authors list (link)
  30. ^ Mike Melanson (mike at (8 December 2004), VP3 Bitstream Format and Decoding Process,, archived from the original on 6 January 2013, retrieved 27 September 2009
  31. ^ Stephen Shankland (1 September 2015). "Tech giants join forces to hasten high-quality online video". CNET. Retrieved 17 March 2021.
  32. ^ a b c Xiph.Org Foundation (24 September 2009), : news, Xiph.Org Foundation, retrieved 25 September 2009
  33. ^ Xiph.Org Foundation (17 September 2004). "Theora I Specification, Foundation, September 17, 2004" (PDF). Archived from the original (PDF) on 28 September 2004. Retrieved 26 September 2009.
  34. ^ "CHANGES file". Retrieved 31 December 2022.
  35. ^ Giles, Ralph (3 November 2008). "Theora 1.0 final release!". theora-dev (Mailing list). Retrieved 4 November 2008.
  36. ^ "The Xiph.Org Foundation announces the release of Theora 1.0" (Press release). Xiph.Org Foundation. 3 November 2008. Retrieved 6 August 2009.
  37. ^ Giles, Ralph (24 September 2009). "libtheora 1.1 (Thusnelda) stable release". theora-dev (Mailing list). Retrieved 24 September 2009.
  38. ^ Monty (18 May 2010). "Theora: Ptalarbvorm project update 20100518". Retrieved 1 July 2010.
  39. ^ McLean, Prince (7 July 2009). "Ogg Theora, H.264 and the HTML 5 Browser Squabble". AppleInsider. Retrieved 1 November 2020.
  40. ^ Larabel, Michael (29 October 2023). "Google Chrome To Remove Theora Video Codec Support". Phoronix. Retrieved 1 November 2023.
  41. ^ "Intent to Ship: Deprecate and remove Theora support". Retrieved 1 November 2023.
  42. ^ "MPEG-4 Codec shoot-out 2002 – 1st installment". Doom9. 2002. Archived from the original on 23 February 2008. Retrieved 19 December 2007.
  43. ^ Codec shoot-out 2005 – Qualification, Doom9, 2005, archived from the original on 31 December 2007, retrieved 19 December 2007
  44. ^ Loli-Queru, Eugenia (12 December 2007). "Theora vs. h.264". OSNews. Retrieved 1 April 2008.
  45. ^ Halbach, Till (March 2009). "Dirac and Theora vs. H.264 and Motion JPEG2000". Archived from the original on 7 July 2012. Retrieved 22 April 2008.
  46. ^ Montgomery, Chris. "Theora "the push for 1.0" update". Retrieved 19 December 2007.
  47. ^ Blizzard, Christopher. "Theora Update 7 May 2009". Retrieved 10 May 2009.
  48. ^ DiBona, Chris (13 June 2009). "H.264-in-<video> vs plugin APIs". whatwg (Mailing list). Retrieved 10 August 2009.
  49. ^ Maxwell, Greg (13 June 2009). "YouTube / Ogg/Theora comparison". Xiph.Org Foundation. Archived from the original on 9 July 2009. Retrieved 10 August 2009.
  50. ^ Merten, Maik (15 June 2009). "Another online-video comparison". Xiph.Org Foundation. Archived from the original on 9 July 2009. Retrieved 10 August 2009.
  51. ^ Richmond, Gary. "Firefogg: Transcoding videos to open web standards with Mozilla Firefox". Retrieved 2 November 2023.
  52. ^ "Xiph Subversion repository: trunk/theora-fpga". Xiph.Org Foundation. Retrieved 10 August 2009.
  53. ^ "XiphWiki: Theora Hardware". Xiph.Org Foundation. Retrieved 10 August 2009.
  54. ^ MozillaWiki (18 March 2009), Firefox3.5/Features, MozillaWiki, retrieved 11 October 2009
  55. ^ Mozilla Corporation (30 June 2009), Mozilla Firefox 3.5 Release Notes, Mozilla Corporation, retrieved 11 October 2009
  56. ^ Mozilla Corporation (9 February 2010), Firefox Mobile Features, Mozilla Corporation, retrieved 9 February 2010
  57. ^ "Mozilla Eyes Removal Of Theora Support In Firefox". Retrieved 1 November 2023.
  58. ^ "1860492 – Investigate removing Theora support". Retrieved 1 November 2023.
  59. ^ Google Chrome to support HTML 5 video, SoftSailor, 28 May 2009, archived from the original on 3 October 2009, retrieved 11 October 2009
  60. ^ Shankland, Stephen (28 May 2009), Google Chrome gets HTML video support, cnet news, retrieved 11 October 2009
  61. ^ Issue 16657: Ensure FFmpeg binaries end up in snapshots on all platforms, Google Chromium, 14 July 2009, retrieved 6 February 2010
  62. ^ Larabel, Michael (7 December 2023). "Chrome 120 Released With Theora Support Evaporating, Adds WebGPU & CSS Improvements". Retrieved 9 December 2023.
  63. ^ "Deprecate and remove Theora support. – Chrome Platform Status". Retrieved 24 October 2023.
  64. ^ Kaiser, Robert (16 September 2009), What's New in SeaMonkey 2.0 Beta 2,, retrieved 11 October 2009
  65. ^ Bugreport: Wish for audio/video element support in Konqueror, 13 May 2007, archived from the original on 28 December 2012, retrieved 2 December 2009
  66. ^ Plans for Konqueror 4.4, 26 November 2009, archived from the original on 17 July 2011, retrieved 2 December 2009
  67. ^ Jägenstedt, Philip (31 December 2009). "(re-)Introducing <video> – Official blog for Core developers at Opera". Opera. Archived from the original on 4 January 2010. Retrieved 2 January 2010.
  68. ^ Arjan van Leeuwen (31 December 2009). "Happy New Year! – Official blog for Core developers at Opera". Opera. Archived from the original on 4 January 2010. Retrieved 2 January 2010.
  69. ^ Experimental Opera-video build with native Ogg Theora support, Opera, 25 April 2007, archived from the original on 2 December 2007, retrieved 11 October 2009
  70. ^ A call for video on the web – Opera <video> release on Labs, Opera, 7 November 2007, retrieved 11 October 2009
  71. ^ "ffmpeg2theora". Archived from the original on 11 March 2008. Retrieved 2 June 2009.
  72. ^ "ffdshow Summary". Retrieved 23 October 2009.
  73. ^ Cutka, Milan (4 October 2002). "Theora support in ffdshow a ffvfw". theora-dev (Mailing list).
  74. ^ "Theora in .ogg no only .avi – ffdshow tryouts Forum". 15 January 2008. Retrieved 23 October 2009.
  75. ^ "GStreamer Base Plugins 0.10 (". Retrieved 23 October 2009.
  76. ^ "GStreamer Base Plugins 0.10 Plugins Reference Manual – Theora plugin library". Retrieved 23 October 2009.
  77. ^ "Ogg Video Tools - Browse Files at". Retrieved 6 November 2022.

External links[edit]